title: Trashing of single-stranded DNA generated during processing of arrested replication fork in E. coli.
abstract: We analyzed formation of single-stranded DNA (ssDNA) related to SOS induction in nalidixilate (Nal)-treated Escherichia coli, using immunofluorescence microscopy accompanied by computer analysis. We found enhancement of both ssDNA concentrations and cells having ssDNA foci that often localized around cellpoles. Analyzing several mutants deficient in DNA repair or replication, we found, after Nal treatment, that recN, recA, uvrD and dnaB failed to increase ssDNA concentration and that recG and particularly ruvA only partially enhanced it. In Nal-treated recB mutant, despite its failure in SOS induction, ssDNA foci positive cells increased with a slight enhancement of its concentration. These observations suggest the existence of a cellular process that sequesters genotoxic ssDNA as inert form, offering a new concept for SOS suppressor genes action.
authors.affiliation: CNRS, UMR7592 Université Denis Diderot Paris 7 Institut Jacques Monod, 15 rue Hélène Brion, 75205 Paris, France; Unité INSERM-1001, Université Paris Descartes*, Sorbonne Paris Cité, F-75205 Paris, France. Electronic address: masamichi.kohiyama@univ-paris-diderot.fr.
authors.forename: Masamichi
authors.initials: M
authors.lastname: Kohiyama
authors.forename: Vincent
authors.initials: V
authors.lastname: Contremoulins
authors.forename: Xavier
authors.initials: X
authors.lastname: Baudin
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication; D004269:DNA, Bacterial / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D055786:Gene Knockout Techniques; D007091:Image Processing, Computer-Assisted; D008856:Microscopy, Fluorescence; D009268:Nalidixic Acid / Q000378:metabolism; D013014:SOS Response, Genetics
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D009268:Nalidixic Acid; D045643:DNA Repair Enzymes
keywords: 4′,6-diamidino-2-phenylindole; 5-bromouracil; 5BU; DAPI; DSB; E. coli; HJ; Holliday Junction; MI; SOS responses; double-strand break; mean intensity; quinolone; single-stranded DNA; ssDNA